Method for making a pavement wearing course



Oct. l, 1929. 1 R. MacKENzlE y METHOD FOR MAKING A `PAVEMENT WEARING COURSE Filed Aug. 6, 1928 is to Patented Oct.. 1 1929' UNITED STATES PATENT OFFICE LEON It. MAUKENZIE, or Das M01-Nas, Iowa Application led August 6, 1928. 4 Serial No. 297,635.

The object of my invention is to provide a method for making a pavement wearing course, whereby it is possible to utilize plastic material, such as asphaltic'or bituminous mix, which are well-known and generally available, in such manner that the finished product will not have that movement within itself, whereby an uneven surface is caused.

Another purpose of my present invention provide such -a pavement, which can be laid quickly and economically with readily available eq'uipment.

An additional purpose is to provide such a wearing course, which is readily adapted for use on any base of sufficient stability to act as such, and which can be employed for re-surfacing old pavements to which it is difiicult to anchor a top course.

It is well known that during the summer months when the air temperature is quite high, asphaltic materials, wear course of a pavement is ordinarily formed, are subjected to easy displacement due to traffic upon the wear course.

The asphaltic materials during the" high temperature of the summer months arecomparatively soft or pliable and due to traffic thereon are very quickly and easily displaced.

It is further well known that asphaltic materials have a greater affinity for heat and the retention of the/same. It thus follows that the heat which/is absorbed within the pavement will give to the pavement a temperature greater orf/higher than the air tempera-ture.

Thedegree or heat within the pavement is retained -for a considerable length of time after the suns heat rays have and it is my object to provide a will eliminate the movement of the asphaltic material within itself.

Specifically, it is my purpose to provide a wear course for pavement, comprising asphaltic or bituminous or other plastic material, having such reinforcing within itself as to prevent abnormal movement of the upper portion of such course with relation to the lower portion, which ordinarily occurs under traiiic and temperature conditions where such material is used.

from which the been absorbed, pavement that For illustrating my invention, I haveY shown drawings herewith, in which Figure 1 is a vertical, sectional view of my wearing course after it is laid and'before completion.

Figure 2 is a vertical, sectional view of the completed pavement; and

Figure 3 is a sectional view showing the respective elements of the wearing course.

As is explained in my co-pending application, Serial N o. 297 ,634, iiled August 6, 1928, the use of asphaltic or bituminous materials for wearing courses of pavements is subject to certain well-recognized objections.

This type of pavement-tends to roll into humps and hollows and to form rough surfaces unsatisfactory for traffic conditions. Especially in warm weather, it tends to ow toward the low spots in the road, particularly at the sides, and especially when subjected-to impact from traffic. After it becomes Vrough and is then continually subjected to traffic impact, it is liable to develop holes. Water gathers in the low spots and always seeps under the wearing course and causes deterioration of the entire pavement wearing course.

Attempts have heretofore been made to anchor the wearing course to the base with some degree of success. l

Chemicals have been used for hardening the wearing course material with rather indifferent success.

I have found that the diiiculties can not be met by anchoring the wearing course to the base. This is true because such plastic wearing course has what may be called an axis of movement within itself. That is to say, even if anchored to the base, the upper portion of the material of the wearing course will tend to roll or move upon the lower portionx with the resulting objectionable high and low spots in the pavement.

It is impossible in practice to make the wearing course so thin as to eliminate the objectionable movement of the material within itself, because when the wearing course is made thin, the volatile oilsithe asphalt are drawn out by the hot sun, and thereafter such `ing graded sand, but no rock aggregate o This movement of the material within itself is not serious or noticeable in the lower inch of its thickness. Above one inch of thickness, it becomes more and'more noticeable and a factor for'destroying the desired contour of the wearing surface. The use of metal reinforcing in such a wearing course has not been practical because of the necessity for raking and fluing, with which the reinforcing seriously interferes.

What I consider thel best of such plastic material wearing courses'have a large rock content. The more the rock-can be pressed together, the better is the pavement and the longer will be its life.

Where there is a large rock content, it is diliicult to force any reinforcing in from above.

I have devised my present method for affording such reinforcing and so relating it to the rock aggregate in the wearing course, as to make it possible to provide a wearing course, high rock content, and in which `the rocks are forced closely together, and are so anchored with relation to each other andthe reinforcing as to practically eliminate any movement of the body of material within itself.

In the practice of my. method, a layer of asphaltic or bituminous material 18, containsubstantial size, is placed upon any suitable pavement base 10. This lower layer 18 is preferably laid hot and is then immediately raked or luffed.

As soon as possible, there is placed upon it, sections of foraminous material, such as expanded metal 14 overlaid or suitably locked together to form a substantially continuous mesh over the surface of the lower layer 18.

Immediately thereafter,v an upper layer 20, which may be of similar material is sperposed upon the reinforcing, and the lower layer, as shown' forfinstance in Figure 1. This also is preferably raked or ufed while hot to bring it to a true contour, and immediately thereafter angular rock is evenly' lspread upon it.

' The thickness of the `lower layer should be suchthat there would be little movement of the body of material within itself at the height of such layer.

The thickness of the upper layer should be such that the stone will be forced into the which when compressed has a veryl wearing course .meshes ofvthe reinforcement by rolling-orY pressure.

The stone should-be angular, hard and of l,

such size that the the upper forced into the plastic material by pressure, as for instance by means of a heavy roller. This rolling will force the stone into the top layer and will force a portion of the stone' into and through the intersticesl of the reinforcement as illustrated in Figure 2.

Therewill thus be formed a completed wearing course in which the material will be so compressed with a large rock aggregate that it `will have what is almost a rock upper surface.

The upper and lower layers will be locked together by 'means' of the stones or rocks which extend into and through the holes in the foraminous reinforcing material.

The monolithic mass-thus provided will have no movement of material within itself sufficient to cause trouble.

The stone for example'or by way of illustration may be of from three-fourths of an inch to one and one-half inches in size, larggreatest dimension would"` be preferably greater than the thickness of' layer 20. The stone should. be Y est dimension, and the mesh may have openings of from two to two and one-half inches, long dimension, and one to one and one-half inches, short dimension..

Any tendency of the upper portion of-the to move with relation to the lower layer would'be ofcourse resisted by the stone projecting from the upper into the lower layer, and also by the engagement of the stone with the material of the reinforcing.

Thus the so-called axis of movement of the materialwithinitself is raised to the upper f part of the upper layer containing the stone.

It is possible with a wearing course for pavement made according to the method here described to provide a product' of suicient thickness, to have proper longevity and wearing qualities andyet from which any substantial movement of the body of material within itself is eliminated.

With such a wearing course, the necessity for anchoring to the base isdone away with, because where there is vno movement of the material of the wearin course within the body thereof, there will o viously be no movement of the wearing course upon the base.

This makes the wearing course made according to this structure adaptable for any base and particularly for worn pavement, which has a smooth surface.

In my claims, I intend to use the words asphalt or asphalticvI to cover bituminous mixt-uresand any plastic material of a kind adapted for the purpose and normally having movement within'A itself when subjected be laid between the. layers and will not interere with luling, and which will coact with the rock aggregate to accomplish the desired y result,

I claim as my invention: v l. A method of making a bituminous pave- -ment comprising the placing upon a suitable base of a layer of asphaltic material then placing upon thisY lower layer a continuous semi rigid`binding mesh anchoring means, then superposing upon the anchoring means and lower layer an upper layer of asphaltic material, then evenly distributing upon the` top layer'a rock aggregate, a substantial portionof which is of a largest dimension slightly greater than the thickness of such top layer when the top layer is compressed, and thereupon forcing such rock into and through the top layer of the course by pressure from above and causing the rock to enter the interstices of the anchoring means for thus interlocking the largest dimension of which is slightly greater than the thickness of the top layer, then rolling said pavement for forcing the. rock aggregate downwardly into the plastic material and into cooperative relation with such anchoring means, wherebv the rock ag-l gregate forced into such relation will be held bv the reinforcing means against lateral movement and will anchor nthe top layer.

placing upon this lower layer of a continuous semi rigid binding mesh anchoring means, then superposing upon the anchoring means and lower layer an upper layer of asphaltic material, then evenly distributing upon the upper layer rock aggregate, then subjecting the completed pavement to pressure from above, thereby forcing a substantial part of the rock aggregate into and through-the top layer of the course and causing such substantial part of the rock aggregate to enter andpartially project through the interstices of the anchoring means for thus interlocking the aggregate, the layers and the anchoring means, and thereby forming a wear course of a matrix of hard rock aggregate to resist abrasion from direct contact with traffic'.

Des Moines, Iowa, July 30, 1928.

LEON R. MACKENZIE.

3. A methodof making a bituminous pavei ment comprising the placing upon a suitable base a layer of asphaltic material and then placing on this lower layer a continuous semi rigid binding mesh anchoring means, then superposing upon theanchoring means and 'lower layer an upper layer of asphaltic material, then evenly distributing upon the upper layer rck aggregate, and thereupon subjecting the pavement to pressure from above, the rock aggregate being in such an amount and of such size that when the pavement is subjected to such pressure a substantial part of the aggregate will be forced into and through the top layer and causedto enter and partially project through the interstices of the anchoring means for thus interlocking the aggregate, the layers and the anchoring means. 4. A method for making a bituminous pavement comprising the placing upon a suitable base of a layer of asphaltic material, the

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